I feel your pain. It's been a mystery to me why Io gets so little attention It's the most geologically active world in our solar system for Pete's sake.

When NASA announced they were studying outer planets moon missions, the four names that keep coming up are Titan, Europa, Ganymede and Enceladus. First in the "what can you get with a billion dollar mission" studies, and then the "well, fine, what do you get for 3 billion?"

Turns out you couldn't do much of anything worthwile with a billion dollars for the listed targets, but I'd wager you could get a lot of bang for your buck if you asked the same question about Io missions.

Io is just a whole order of magnitude more difficult to do, in-close. The radiation environment there is extraordinary. The surface conditions on most of the globe are straight from Dante's Inferno. Orbiters and landers would be fried extremely fast.

You almost have to do your Io science from something of a distance.

-the other Doug

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“The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain

No you just have a Jupiter orbiter make repeated flybys, and I would imagine it could be done more cheaply than some of these flagship mission. In fact, the one good thing going for a Europa mission, IMHO, is that it could be used to test a lot of rad-hard technologies needed for an Io mission

Incidentally, I think on the first one, they got the apparent motion of Jupiter completely backwards while moreover depicting Jupiter as tidally locked WRT the Sun (or somehow otherwise rotating other than the way it actually does).

Io is just a whole order of magnitude more difficult to do, in-close. The radiation environment there is extraordinary. The surface conditions on most of the globe are straight from Dante's Inferno. Orbiters and landers would be fried extremely fast.-the other Doug

I agree that doing an Io Orbiter or lander would be really expensive. And the science payload on something like JSO is also very heavy and very expensive.

I was specifially reffering to the Billion Dollar mission class.... essentially a bit of a beefed up New Frontiers budget. For that price you could reasonably do a three axis stabilzed, moderately instrumented probe. Put it into a highly elliptical orbit and make repeated encounters. A single such flyby would return more data than Galileo did over it's entire mission. Even if the probe's electronics can only handle 10-20 flybys (which is roughly what Juno is designed for, IIRC) that is a hell of a science return.

I keep hoping Europe would step up to that plate, see a chance to do some exciting science that the US wasn't interested in. Unfortunately they appear to have been hi-jacked by the Europa Mafia. They are also looking for partners. If that results in us somehow managing to afford both Titan and a Europa mission in the next 20 years, horay.

Otherwise.... shame they didn't jump at Io while we were engaged elsewhere. Or at just about anything in the outer planets... there are so many lonely targets out there. Bare Bones Uranian Orbiter anyone? Anyone?

I was specifially reffering to the Billion Dollar mission class.... essentially a bit of a beefed up New Frontiers budget. For that price you could reasonably do a three axis stabilzed, moderately instrumented probe. Put it into a highly elliptical orbit and make repeated encounters. A single such flyby would return more data than Galileo did over it's entire mission. Even if the probe's electronics can only handle 10-20 flybys (which is roughly what Juno is designed for, IIRC) that is a hell of a science return.

If if I remember the JSO report, they concluded that another Galileo-style orbiter would add enough understanding of the Galilean moons to be useful. An orbiter would be needed to get at the next level of questions. The EE report explicitly states that the key questions for Europa cannot be answered with flybys.

I personally disagree. Not only did Galileo have very limited data return, its instruments were vintage 1975ish. Flying modern instruments would tell us a lot more. What would be lost for Europa would be the ability, as I read the report, to really nail down where to send a lander. Since the first lander will be able to study only the surface and near sub-surface, its really important to know where the surface has most likely interacted recently with the deeper subsurface. Also, it's essential to understand the terrain at ~1m scales to characterize lander safety issues.

As for the cost of a Galileo repeat, I think that if it goes into the inner Jovian system, it may not fit within the budget of a New Frontiers. Juno fills the budget, doesn't have radioisotope power sources, and has modest radiation hardening. A Galileo repeat would have all those. A craft that stayed out near Ganymede with maybe a few Europa flybys might avoid the need for these budget busting features. It could also have even a larger camera than what JSO is proposed to carry for remote studies of Io (which I find fascinating).

My emerging view is that the Jovian system is important to understand -- it seems to be a common planetary type around other stars. I think that a modest Galieo- style orbiter combined with a much less capable Europa orbiter a la the ESA makes sense as the next step. Studying that system, though, is just too hard because of the radiation and landers on Europa in interesting places is likely to be really hard -- there's lots of rough terrain. So I'd keep my investments in Jovian craft modest. And then I'd put my big money into Titan where the moon is endlessly fascinating, there's no radiation, and a wonderful atmosphere to simplify landing or floating about.

Basically, I just wanted to let Volcanopele know he is not a lone voice in the wilderness. Others of us have wondered why Io never even gets a passing mention.

I find Io endlessly fascinating. Given the incredible difficulty of any intense study of any single moon, I'd put my money into a mission that studies the differences. Yes, it is a Galileo repeat, but MRO is a Viking orbiter repeat in the same sense.

In depth studies of any single moon, though, is just too hard. If we find a good location on Europa, can we afford a lander to follow up? Can we even technologically implement it?

sorry to disappoint you thin-skinned, er i mean thin-shelled people. europas shell is thick, at least 10 more likely 20 km.the smoking gun is the topography. there are places with 1 kilometer of relief in very short distances. one such scarp has a slope of around 30 degrees. a shell only a few kilometers thick simply cant generate or support such a large topographic height.

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